1. Reverse Direction in 802.11ac
Feb, 2008
doc.: IEEE /xxxx
Date: September 2010
Reverse Direction in ac
Date:
Authors:
L. Chu et al
Liwen Chu, STMicroelectronics

2. Date: September 2010
Reverse Direction in n
RD gives an opportunity for a responder to transmit data to an initiator during the initiator’s TXOP.
RD aggregates data with response control MPDUs.
RD reduces Contention.
RD is more effective in increasing TCP/IP performance.
DL-SDMA is a key technology to improve the overall ac network performance.
It is advisable to implement RD in AC.

3. Reverse Direction in 802.11n (Cont’d)
Date: September 2010
Reverse Direction in n (Cont’d)
In HT Extended Capabilities field, RD Responder subfield is used to indicate if a STA supports for acting as a reverse direction responder.
In HT Control field, AC Constraint is used to indicate if the response to a reverse direction grant (RDG) may contain data frames from any TID.
In HT Control field, the RD initiator uses RDG/More PPDU subfield to indicate if reverse transmission is granted.
In HT Control field, the RD responder uses RDG/More PPDU subfield to indicate if the PPDU carrying the frame is followed by another PPDU.
802.11AC does not have HT Extended Capabilities field and HT Control field.

4. Date: September 2010
Solutions
In Extended Capabilities field, RD Responder subfield is added. The added field has the same meaning of RD Responder field in HT Extended Capabilities field.
The carrying of AC Constraint subfield and RDG/More PPDU subfield:
If HTC control field is used by ac, the AC Constraint subfield and RDG/More PPDU subfield in HTC can be used without change.
If new VHTC control field is defined by ac, the AC Constraint subfield and RDG/More PPDU subfield in HTC can be be added.
Otherwise in VHTSIGB or VHTSIGA, AC Constraint subfield and RDG/More PPDU subfield are added. The added fields have the same meaning of AC Constraint subfield and RDG/More PPDU subfield in HT Control field.
Adding AC Constraint subfield and RDG/More PPDU subfield to VHTSIGA means that reverse operation is not allowed immediate following DL-MU frame.
The current reverse direction protocol defined in subclause 9.15 can be used without further change.

5. Date: September 2010
Straw Poll
Do you support adding the following item into the specification framework document, 11-09/0992?
6.4: Reverse Direction shall be included in the specification to improve the MAC efficiency.